Catalytic cracking of residual hydrocarbons



Nov. 22, 1949 .1. DELATTRE-SEGUY 2,488,713.

CATALYTIC CRACKING OF RESIDUAL HYDROCARBONS Filed May 1, 1947 Sfr/bper Fracfionafor Regenerafor k S Q:

IN VEN TOR. Jean De/af/ra Seguy Aria/nay Patented Nov. 22,1949

CATALYTIC CRACKING OF RESIDUAL HYDROCARBONS Jean Delattrc-Seguy, Washington, D. 0., assignor to Universal (Bil Products Company, Chicago, 111., a corporation of Delaware Application May 1, 1947, Serial No. 745,315

4 Claims.

This invention relates to the catalytic cracking of hydrocarbons. It is more particularly .concerned with the conversion of high boiling hydrocarbons suoh as topped or reduced crudes to high octane number gasolines by a two step process employing fluidized catalyst.

In order to obtain a greater amount of gasoline from a given amount of crude oil, it is necessary to crack the heavier or residual portions of the crude. To utilize these high boiling fractions as charging stocks for catalytic cracking processes, it has been necessary in the past to remove the coke-forming constituents, such as asphaltenes and the like, by relatively expensive methods such as propane deasphalting, vacuum distillation, and steam distillation. Even then the resultant material often was found to be an undesirable charge stock, particularly in fluid catalyst systems, because it was difficult to vaporize and process, and because it cracked to excessive amounts of low grade products such as coke or gas when contacted with active, freshly regenerated catalyst.

I have invented an improved economical process for cracking residual oils to good yields of gasoline without excessive production of gas or coke, and without prior treatment or removal of asphaltenes and the like from the oil.

In one embodiment my invention relates to a catalytic cracking process which comprises subjecting a heavy reflux condensate, produced as hereinafter described, to the action of freshly regenerated cracking catalyst at cracking conditions in a first cracking zone, separating the catalyst from the hydrocarbons in said zone, passing the catalyst so separated to a second cracking zone wherein it is contacted with residual oil and a light reflux condensate, produced as hereinafter described, at cracking conditions, separating the catalyst from the hydrocarbons in said second zone, passing the catalyst s separated to a regeneration zone wherein the carbonaceous deposit is burned from the catalyst, supplying the hot regenerated catalyst to said first zone, combining the hydrocarbon efiluents from said cracking zones, fractionating the same to obtain a light and a heavy reflux condensate boilin above the gasoline range, and recycling at least a portion of the light reflux condensate to the second cracking zone and recycling at least a portion of the heavy reflux condensate to the first cracking zone.

In a more specific embodiment my invention relates to a catalytic cracking process which comprises subjecting a heavy reflux condensate, pro duced as hereinafter described, to the action of freshly regenerated cracking catalyst at relatively severe cracking conditions in a first zone, sepa rating the catalyst from the hydrocarbons in said zone, passing'the catalyst so separated to a sec-' ond zone wherein it is contacted with reduced crude and a light reflux condensate, produced as hereinafter described, at cracking conditions less severe than those maintained in said first zone, separating the catalyst from the hydrocarbons in said second zone, passing the catalyst so separated to a regeneration zone wherein the carbonaceous deposit is burned from the catalyst, supplying the hot regenerated catalyst to said first zone, combining the hydrocarbon efiluents from said cracking zones, fractionating the same to obtain a light and a heavy reflux condensate boiling above the gasoline range, and recycling at least a portion of the light reflux condensate to the second cracking zone and recycling at least a portion of the heavy reflux condensate to the first cracking zone.

Briefly stated, my invention comprises cracking a reduced crude or like material, together with a liquid reflux condensate, in the presence of partially spent cracking catalyst at relatively mild conditions in one zone. The catalyst is separated from the cracked products and is regenerated in another zone. A heavy reflux condensate is then cracked in the presence of the freshly regenerated catalyst in a third zone at relatively severe c0nditions. The partially spent catalyst from this zone is separated from the hydrocarbons therein and is passed to the first zone. This process has several advantages. The first is that the residual oil, such as reduced crude or topped crude, is contacted with partially spent catalyst at relatively mild conditions, which results in moderate cracking to lower boiling hydrocarbons without overcracking or excessive coke production. Somev of the light reflux condensate is converted to gasoline, thus increasing the yield of said product. Furthermore, the presence of the light condensate in this zone apparently helps to reduce the yield of gas and coke that normally would be obtained from cracking crude residue alone. A second advantage lies in the fact that the heavy reflux condensate is cracked at relatively severe conditions which result in high conversions to high octane number gasoline. ,Relatively intense cracking conditions are feasible in this step be,

cause the coke-forming tendency of the heavy reflux condensate is small, in fact it is considerably less than that of the residual oil. Another advantage of this sequence of steps is that it permits better utilization of the sensible heat of the regenerated catalyst, since the cracking of the heavy reflux condensate is conducted at a higher temperature than is the cracking of the residual oil plus the light reflux condensate. Thus, by the particular serial flow of catalyst utilized here, the hot, freshly regenerated catalyst is sent to the high temperature cracking zone wherein its temperature is lowered in supplying heat for raising the temperature of and vaporizing the feed thereto, and in supplying the heat of reaction. The partially carbonized and cooled catalyst withdrawn from this zone still is at a fairly high temperature and has an appreciable heat content. Use is made of a portion of this residual heat content in the low temperature cracking zone. A further advantage of my process lies in the fact that, although there are two separate cracking zones, only one regenerator is employed for reactivating the catalyst.

Further objects and advantages of my process will be apparent from the following description of the accompanying drawing which illustrates in conventional side elevation one form of apparatus inwhich the present invention may be accomplished. For purposes of simplification, certain auxiliary equipment such as pumps, condensers, reflux accumulators, and the like have been omitted from the drawing but it is to be understood that such equipment is to be used wherever engineering skil1 dictates.

Hot regenerated catalyst in a fluidized form, such as powder or microspheres, present in regenerator I is passed through line 2 containing valve 3 into line 4 wherein it is picked-up by a stream of heav reflux condensate produced as hereinafter described. The mixture of catalyst and oil is directed through line 4 into the lower portion of reactor 5 and is substantially uniformly distributed over the cross sectional area of the reaction chamber by means such as perforated plates or grids horizontally disposed therein.

Any suitable metal oxide cracking catalyst such as silica-alumina, silica-zirconia, silicaalumina-zirconia, silica-magnesia, silica-aluminamagnesia, alumina-magnesia, alumina-bcria, and the like, may be employed. These catalysts may be prepared in any suitable manner including separate, successive, and coprecipitation methods. In some cases naturally occurring materials such as montmorillom'te or acid treated montmorillonite may be employed.

A dense phase bed of solid catalyst particles is maintained in reactor 5 and is kept in a fluid-like state of relatively high density by the hydrocarbons passing upwardl through the bedat a velocity which partially counteracts the force of gravity on the solid particles and brings about their hindered settling within the dense phase bed. Above the dense phase bed in the upper portion of the reaction chamber a relatively light phase region having a reduced catalyst density is maintained, wherein the catalyst is substantially separated from the hydrocarbons by means of a separator, such as a cyclone separator, not shown on the drawing. The cracked products are discharged from the upper end of reactor 5 through line 6 containing valve I and are directed through line 6 into fractionator 9.

Relatively severe operating conditions are maintained in reactor 5. These conditionsusu ally are a. temperature of from about 940 F. to

about 1100 F.; a weight hourly space velocity, defined as the weight of hydrocarbon charged to the reactor per hour divided by the weight of the catalyst in the reactor, of from about 0.2 to about 2.0; and a relatively high catalyst to oil weight ratio, usually greater than 5.

Partially carbonized catalyst is withdrawn from reactor 5 through line I0 containing valve II and is passed into line I3 wherein it commingles with a stream of light reflux condensate produced as hereinafter described. If desired, a stripping medium such as steam or other inert gas may be passed into line I0 through line I4 containing valve I5 and passed upwardly and countercurrently to the descending stream of catalyst in line I9. It is not essential that the hydrocarbons absorbed on the catalyst be removed by stripping at this stage since such hydrocarbons may be removed in a subsequent stripping operation. A mixture of catalyst and oil in line I3 is directed into the lower portion of reaction zone I6 and is substantially uniformly distributed over the cross sectional area in the manner described in connection with reactor 5.

A. dense phase bed and a light phase region of solid catalyst particles is maintained in reactor !6 in a manner similar to that maintained in the other reactor. Substantially liquid reduced crude or other residual oil is injected into the lower portion of the dense phase in reactor I6 through line I? containing valve I8. The conversion products, from which entrained catalyst has been separated, by means not shown, are discharged from reactor I6 through line I 9 containing valve 29 and are directed through line B into fractionator 9.

The operating conditions maintained in reactor Iii are less severe than those maintained in reactor 5. For example, the temperature usually lies within the range of from about 825 F. to about 950 F., the weight hourly space velocity usually lies Within the range of from about 1.5 to about 6.0, and the catalyst to oil weight ratio usually is low. Although some of these ranges overlap the ranges designated for reactor 5, the process is operated in such a manner that the cracking conditions in reactor I6 are less severe than those maintained in reactor 5.

The catalyst in reaction zone I5 is withdrawn through line 2I containing valve 2?. and is passed into regenerator I. A stripping medium is passed into line 2! through line 23 containing valve 2 2. The oxidizing gas employed for burning the combustibles on the contaminated catalyst is supplied to regenerator I through line 25 containing valve 25'. Itmay be distributed across the regeneration zone by means of perforated plates or grids. The flue gases are discharged from the upper end. of the regeneration chamber by means or" lineJZl' containing valve 23 and passed through a suitable catalyst separation apparatus.

Although the flow of catalyst and oxidizing gas is shown to be countercurrent in the drawing, saidflow, if desired, may be concurrent, i. e., the catalyst from line 2| may be picked up by the oxidizing medium and transported to the bottom of regenerator I.

The arrangement of the reactors may be modifled if desired. For example, reactor 5 may be superimposed upon reactor I6. If this is done, the catalyst passing from reactor 5 to reactor I6 may do so by means of gravity flow.

In fractionator 9, the hydrocarbon efiluents from the reactors are separated into several fractions. Gasoline and gaseous hydrocarbons are rected into the bottom of stripper 33 through line 34 containing valve 85. This medium flows upwardly and countercurrently to the descending stream of light reflux condensate and removes gasoline and gaseous hydrocarbons therefrom. These latter materials pass overhead from the stripper and are directed back into fractionator 9 through line 36 containing valve 3'5. The stripped light reflux condensate is directed from stripper 33 through line l3 containing valve 38. A portion of this stream may be directed to storage or other conversion processes through line 39 containing valve 40. In the event that additional heat is required in the process in order to maintain a satisfactory heat balance, the light reflux condensate passing through line [3 may be heated or vaporized by means not shown in the drawing.

Heavy reflux condensate is withdrawn from the bottom of fractionator 9 through line 4 containing valve 4|. If desired, this stream may be heated by means not shown in the drawing. Also, a portion of it may be withdrawn to storage or other conversion processes through line 42 containing valve 43. In order to balance out the process, it may be necessary or desirable to pass a portion of the light reflux condensate to reactor 5 or a portion of the heavy reflux condensate to reactor l6. This may be done by directing a portion of one or the other of the streams through line 44 containing valve 45.

In general, the pressures maintained on the reactors and the regenerator will lie below 100 p. s. i. and preferably below 50 p. s. i.

I claim as my invention:

1. A catalytic cracking process which comprises subjecting a heavy reflux condensate, boiling above the gasoline range and produced as hereinafter described, to the action of freshly regenerated cracking catalyst at cracking conditions in a first cracking zone to thereby crack at least a portion of said condensate and to partially carbonize said catalyst, separating the partially carbonized catalyst from the hydrocarbons in said zone, passing the catalyst so separated without regeneration or substantial cooling thereof to a second cracking zone wherein it is contacted with residual oil and a light reflux condensate, boiling above the gasoline range and produced as hereinafter described, at cracking conditions, sep- 7 2. A catalytic cracking process which comprises subjecting a heavy reflux condensate, boiling above the gasoline range and produced as hereinafter described, to the action of freshly regenerated cracking catalyst at relatively severe cracking conditions in a first cracking zone to thereby crack at least a portion of said condensate and to partially carbonize said catalyst, separating the partially carbonized catalyst from the hydrocarbons in said zone, passing the catalyst so separated without regeneration or substantial cooling thereof to a second cracking zone wherein it is contacted with residual oil and a light reflux condensate, boiling above the gasoline range and produced as hereinafter described, at cracking conditions less severe than those maintained in said first cracking zone, separating the catalyst from the hydrocarbons in said second cracking zone, passing the catalyst so separated to a regeneration zone wherein the carbonaceous deposit is burned from the catalyst, supplying the hot regenerated catalyst to said first cracking zone, combining the hydrocarbon effluents from said cracking zones, fractionating the same to obtain a light and a heavy reflux condensate boiling above the gasoline range, and recycling at least a portion of the light reflux condensate to the second cracking zone and recycling at least a portion of the, heavy reflux condensate to the first cracking zone.

3. The process of claim 2 further characterized in that the temperature maintained in the first zone is higher than the temperature maintained in the second zone.

4. A catalytic cracking process which comprises subjecting a heavy reflux condensate, boiling above the gasoline range and produced as hereinafter described, to the action of freshly regenerated cracking catalyst at a temperature of from about 940 F. to about 1100 F. and a weight hourly space velocity of from about 0.2 to about 2.0 in a first cracking zone to thereby crack a portion of said condensate and to partially carbonize said catalyst, separating partially carbonized catalyst from the hydrocarbons in said zone, passing catalyst so separated without regeneration or substantial cooling thereof to a second cracking zone wherein it is contacted with residual oil and a light reflux condensate, boiling above the gasoline range and produced as hereinafter described, at a temperature of from about 825 F. to about 950 F. and a weight hourly space velocity of from about 1.5 to about 6.0, separating catalyst from the hydrocarbons in said second zone, passing catalyst so separated to a. regeneration zone wherein the carbonaceous deposit is burned from the catalyst, supplying hot regenerated catalyst to said first zone, combining the hydrocarbon efiiuents from said cracking zones, fractionating the same to obtain a light and a heavy reflux condensate boiling above the gasoline range, and recycling at least a portion of the light reflux condensate to the second cracking zone and recycling at least a portion of the heavy reflux condensate to the first cracking zone.

JEAN DELATTRE-SEGUY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Date 

